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Solute drag-controlled grain growth in magnesium investigated by quasi in-situ orientation mapping and level-set simulations

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Journal of Magnesium and Alloys 2023年第7期11卷 2312-2325页

作者： risheng pei Yujun Zhao Muhammad Zubair Sangbong Yi Talal Al-Samman Institut für Metallkunde und Materialphysik RWTH Aachen University52056 AachenGermany Institute of Materials and Process Design Helmholtz-Zentrum Hereon21502 GeesthachtGermany Department of Metallurgical and Materials Engineering Faculty of ChemicalMetallurgical&Polymer EngineeringUniversity of Engineering&Technology(UET)LahorePakistan Institute for Materials Ruhr-Universität Bochum44801 BochumGermany

Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size *** atoms that favorably segregate to grain boundaries produce a pinning atmosphere that exerts a drag pressure on the boundary motion,which strongly affects the grain growth behavior during *** the current work,the characteristics of grain growth in an annealed Mg-1 wt.%Mn-1 wt.%Nd magnesium alloy were investigated by advanced experimental and modeling *** quasi in-situ orientation mappings with a scanning electron microscope were performed to track the evolution of local and global microstructural characteristics as a function of annealing *** segregation at targeted grain boundaries was measured using three-dimensional atom probe ***-set computer simulations were carried with different setups of driving forces to explore their contribution to the microstructure development with and without solute *** results showed that the favorable growth advantage for some grains leading to a transient stage of abnormal grain growth is controlled by several drivers with varying importance at different stages of *** longer annealing times,residual dislocation density gradients between large and smaller grains are no longer important,which leads to microstructure stability due to predominant solute *** fluctuations in residual dislocation energy and solute concentration near grain boundaries cause different boundary segments to migrate at different rates,which affects the average growth rate of large grains and their evolved shape.

关键词： Magnesium alloys Grain growth Quasi in-situ EBSD Level-set simulation Solute drag Dislocation density gradient

Plastic instability and texture modification in extruded Mg-Mn-Nd alloy

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Journal of Magnesium and Alloys 2022年第1期10卷 160-174页

作者： Sang Kyu Woo risheng pei Talal Al-Samman Dietmar Letzig Sangbong Yi Magic-Magnesium Innovation Center Institute for Materials and Process DesignHelmholtz-Zentrum GeesthachtGeesthacht 21502Germany Institut für Metallkunde und Materialphysik RWTH Aachen UniversityAachen 52056Germany

Even though Mg alloys containing Mn and rare earth elements lead to higher ductility and lower yield asymmetry due to the weak texture after extrusion, plastic instability, commonly known as the Portevin–Le Chatelier(PLC) effect, causes unexpected fragility in the service environment. In the present study, the PLC phenomenon and texture development during the deformation of Mg-Mn and Mg-Mn-Nd extruded alloys were investigated under various temperatures and strain rates. The addition of Nd causes not only texture weakening but also severe PLC phenomenon. The PLC phenomenon was significantly affected by the temperatures and the strain rates, which causes a difference in mechanical properties and development of texture. In the conditions of high temperature and low strain rate, the strength increased while the elongation decreased significantly, and obvious PLC phenomenon with severe serration and negative strain rate sensitivity. The initial texture was maintained even after deformation only under severe PLC conditions, and this is due to the restriction of basal slip and suppression of lattice rotation in PLC conditions. The series of results indicate that the PLC phenomenon causes a reduction of formability even at high temperature.

关键词： Magnesium Plastic instability Portevin–Le Chatelier effect Manganese Neodymium Texture

Effects of Ca and Nd addition on plastic instability in extruded Mg-Mn alloy deformed under various conditions

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Journal of Magnesium and Alloys 2023年第2期11卷 543-552页

作者： Sang Kyu Woo risheng pei Talal Al-Samman Dietmar Letzig Sangbong Yi Institute of Materials and Process Design Helmholtz-Zentrum hereon21502 GeesthachtGermany Institut für Metallkunde und Materialphysik RWTH Aachen University52056 AachenGermany

Plastic instability, called Portevin-Le-Chatelier(PLC) effect, manifests itself as an unstable plastic flow during tensile tests of structural materials. This phenomenon has a strong influence on diverse properties, leading to unexpected vulnerabilities in the service *** various magnesium-based alloys, PLC phenomenon is most prominently observed in the Mg-Mn-Nd alloy under elevated temperature and low strain rate conditions. An important aim of the study is to clarify and compare the significance of the RE and Ca addition, which are known to cause a formation of a largely weakened non-basal type texture, in the occurrence of plastic instability. Due to the PLC phenomenon, there is a risk of weakening texture and formability improvement by the addition of RE and Ca elements in Mg alloys. Based on the understanding of the role of Nd to the PLC phenomenon in Mg-Mn alloy identified in previous studies, the PLC characteristics according to alloying elements and deformation conditions were compared and analyzed. To identify the micromechanical mechanisms of the PLC phenomenon, varies in the microstructure and mechanical properties during deformation of Mg-Mn binary and Ca or Nd-containing Mg-Mn-based ternary alloys in various conditions were systemically analyzed. The addition of Ca did not show a marked PLC effect due to the formation of low number density Mn-Ca and Ca-Ca solute clusters and an unbalanced Mn:Ca ratio. In contrast, the addition of Nd leads to the formation of a higher number density of Nd-Nd and Mn-Nd solute clusters than that of Ca-Ca and Mn-Ca solute clusters of the Mg-Mn-Ca alloy, resulting in a stable solute-dislocation interaction atmosphere under specific ranges of deformation temperature and strain rate. The deformation in the regime of PLC phenomenon, results in a decrease in ductility and an increase in strength, despite deformation at elevated temperatures with maintaining the weakened texture.

关键词： Magnesium Plastic instability Portevin-Le Chatelier effect Solute cluster Neodymium Calcium

The role of recrystallization and grain growth in optimizing the sheet texture of magnesium alloys with calcium addition during annealing

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Journal of Magnesium and Alloys 2020年第1期8卷 252-268页

作者： Fei Guo risheng pei Luyao Jiang Dingfei Zhang Sandra Korte-Kerzel Talal Al-Samman College of Materials Science and Engineering Chongqing University of Technology400054 ChongqingChina Chongqing Key Laboratory of Mold Technology Chongqing University of Technology400054 ChongqingChina Institut für Metallkunde und Metallphysik RWTH Aachen University52056 AachenGermany College of Materials Science and Engineering Chongqing University400044 ChongqingChina

The contribution of recrystallization and grain growth to the texture evolution in AZ31 alloy and a modified version AZ31+0.5 wt.%Ca was investigated utilizing a multi-step annealing *** results showed that the addition of Ca triggered a considerable texture modification by increasing the texture spread and decreasing the overall texture *** effect was found to be temperature *** the annealing temperature remained lower than 450℃,a weak double peak texture with large basal pole tilt towards the RD was *** is correlated to microstructure observations of a large number of Ca-containing nano-sized particles that seemed to suppress grain growth below 450℃,which stabilized the weak recrystallization *** favorable texture was lost upon annealing at higher *** AZ31,recrystallization nuclei were found to preserve the orientation of their deformed parents,which offered limited potential to optimize the texture via annealing *** growth of recrystallized grains resulted in a distinct sheet texture transition from a double-peak to a single-peak basal *** of grain boundary energy and grain topology are discussed to explain the growth advantage of the sharp basal component over other orientations.

关键词： Magnesium alloys Microstructure Texture Recrystallization Grain growth

Rolling texture development in a dual-phase Mg-Li alloy:The role of temperature

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Journal of Magnesium and Alloys 2023年第8期11卷 2980-2990页

作者： Xiaoyan Li Fei Guo Yanlong Ma Luyao Jiang Hongliang Lai Haiding Liu Dingfei Zhang risheng pei College of Materials Science and Engineering Chongqing University of TechnologyChongqing 400054China Chongqing Materials Research Institute Co. LtdChongqing 400707China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Institut für Metallkunde und Metallphysik RWTH Aachen UniversityAachen 52056Germany

Dual-phase Mg-Li alloys sheets were rolled at four different temperatures ranging from liquid nitrogen to 300℃to explore effect of rolling temperature on texture and mechanical properties of the *** plasticity simulation was utilized to illustrate the influence of slip activity on rolling texture *** results show that the rolling texture is largely depended on deformation *** commercial Mg alloys,the critical resolved shear stress of basal slip inα-Mg phase of Mg-Li alloy decreased more significantly by increasing temperature compared to that of pyramidal*** of basal slip by increasing temperature triggered a decrease of split angle of basal poles for the double-peak ***slip largely enhanced by increasing temperature upon 200℃,which induced a wider orientation spread along the transverse *** theβ-Li phase,the promotion of{110}slip system at elevated temperature triggered the enhancement of{211}and{111}texture *** cryo-rolled sample exhibited the highest strength compared to the others due to a strong hardening behavior at this temperature.A two-stage hardening behavior was observed in these as-rolled dual-phase *** transition at phase boundaries could be the reason for appearance of this two-stage hardening.

关键词： Magnesium-Lithium alloys Dual-phase Texture Slip behavior Mechanical properties

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新型育苗基质在烟叶生产中的应用初报

中国农学通报 2009年第9期25卷 102-105页

作者：唐绅杨全柳高春洋胡卫东胡日生黄石旺王沛中国烟草中南农业实验站永州基地湖南永州425000 永州市烟草科学研究所湖南永州425000 中国烟草中南农业实验湖南长沙410028 永州市农业科学研究所湖南永州425000

为减少目前烤烟漂浮育苗对草炭的依赖,开展了完全替代草炭的新型育苗基质研究,并就筛选出的两种基质与目前使用的基质(对照)进行了育苗、田间对比试验。结果表明:两种基质对烤烟种子的出苗期与对照相比基本无影响,但出苗后T1的长势最差... 详细信息

为减少目前烤烟漂浮育苗对草炭的依赖,开展了完全替代草炭的新型育苗基质研究,并就筛选出的两种基质与目前使用的基质(对照)进行了育苗、田间对比试验。结果表明:两种基质对烤烟种子的出苗期与对照相比基本无影响,但出苗后T1的长势最差,T2与对照的差异不大。出苗率以对照最高,其次为T2,T1的出苗率最差;T2的烟苗素质与对照相当,且优于T1,主要体现在烟苗的侧根数目上。T2的产量、产值、均价、上等烟率等经济性状表现最高,但与对照的差异不显著。

关键词：新型基质草炭替代烤烟

1916-1917年殷承瓛出任川边镇守使及其治边探析

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西藏研究 2020年第2期 56-63页

作者：裴儒弟北京师范大学历史学院北京100875

殷承瓛是民国时期著名的滇军将领,1916年护国战争胜利后,滇军据川,前任川边镇守使刘锐恒下台,四川督军蔡锷举荐殷承瓛出任川边镇守使。殷承瓛上任后,积极经营川边,如查办"傅青云叛乱"事件、整治粮税积弊、管理宗教事务等,在一定程度上... 详细信息

殷承瓛是民国时期著名的滇军将领,1916年护国战争胜利后,滇军据川,前任川边镇守使刘锐恒下台,四川督军蔡锷举荐殷承瓛出任川边镇守使。殷承瓛上任后,积极经营川边,如查办"傅青云叛乱"事件、整治粮税积弊、管理宗教事务等,在一定程度上维护了川边稳定。然而,1917年川滇混战,接着彭日升派边军围困打箭炉,殷承瓛孤立无援,被迫辞职,从而其治理川边的计划没有完全付诸实施。因此,殷承瓛在任期间,川边治理的整体成效并不显著。

关键词：川边镇守使殷承瓛治理川边

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湘烟7号烘烤过程中烟叶失水和色素降解特性

作物杂志 2022年第5期 174-179页

作者：朱林曹想邓小华胡日生裴晓东向世鹏肖志君王卫民章程江智敏湖南农业大学农学院湖南长沙410128 中国烟草中南农业试验站湖南长沙410004 湖南省烟草公司长沙市公司湖南长沙410011 浙江中烟工业有限责任公司浙江杭州310008

为明确湘烟7号在烘烤过程中烟叶失水和色素降解的特性,以云烟87为对照,采用电烤箱试验方法,探究不同部位烟叶的叶片与叶脉失水特性及叶绿素与类胡萝卜素的降解特性。结果表明,湘烟7号叶片失水高峰早于对照;湘烟7号中、下部叶易烤特性优... 详细信息

为明确湘烟7号在烘烤过程中烟叶失水和色素降解的特性,以云烟87为对照,采用电烤箱试验方法,探究不同部位烟叶的叶片与叶脉失水特性及叶绿素与类胡萝卜素的降解特性。结果表明,湘烟7号叶片失水高峰早于对照;湘烟7号中、下部叶易烤特性优于对照,上部叶相反;在变黄前期(24h),湘烟7号叶绿素a降解速率显著低于对照,而叶绿素b相反;湘烟7号与对照的叶绿素降解量差异不显著;湘烟7号的类胡萝卜素降解速率和降解量显著低于对照。可见,湘烟7号烘烤过程中烟叶失水和色素降解具有一定的独特性,需依据该品种烘烤特性制定适宜的烘烤工艺,以发挥其质量潜势。

关键词：烤烟失水特性色素降解特性湘烟7号烘烤特性

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稻茬烤烟主栽品种上部烟叶的烘烤特性研究

安徽农业大学学报 2023年第2期50卷 364-371页

作者：朱林张仲文张文军章程裴晓东江智敏肖志君胡日生曹想邓小华湖南农业大学农学院长沙410128 浙江中烟工业有限责任公司杭州310008 湖南省烟草公司长沙市公司长沙410011 中国烟草中南农业试验站长沙410004

为了明确稻茬烤烟主栽品种上部烟叶烘烤特性,给稻茬烤烟制定烘烤工艺提供参考,采用暗箱方法和密集烤房“中温中湿”烘烤工艺,探索了湖南稻作烟区主栽品种K326、云烟87和湘烟7号上部烟叶变黄变褐特性、失水特性、叶绿素降解特性、多酚氧... 详细信息

为了明确稻茬烤烟主栽品种上部烟叶烘烤特性,给稻茬烤烟制定烘烤工艺提供参考,采用暗箱方法和密集烤房“中温中湿”烘烤工艺,探索了湖南稻作烟区主栽品种K326、云烟87和湘烟7号上部烟叶变黄变褐特性、失水特性、叶绿素降解特性、多酚氧化酶活性及淀粉和还原糖含量的变化。结果表明:(1)暗箱试验中湘烟7号、云烟87和K326上部烟叶变黄时间均为40 h;湘烟7号与云烟87褐变时间均为60 h,K326为72 h;3个品种变黄速率差异不显著,K326变褐指数较小。(2)叶绿素降解率为K326>湘烟7号>云烟87,降解均匀度为K326>湘烟7号>云烟87。(3)上部烟叶失水速率为云烟87>K326>湘烟7号。(4)在烘烤变黄期(0~48 h),叶绿素降解量为K326>湘烟7号>云烟87;烘烤末期,湘烟7号的类胡萝卜素降解量最大,K326与云烟87接近。(5)PPO活性的变化规律一致,湘烟7号上部烟叶第1个峰值与云烟87一致,较K326晚12h;湘烟7号第2个峰值出现时间与K326一致,较云烟87晚12h;K326、湘烟7号和云烟87的多酚氧化酶活性平均值分别为0.125、0.127和0.123 U。(6)淀粉降解率为湘烟7号>K326>云烟87;K326、湘烟7号和云烟87的还原糖含量变化类似。综上所述,湖南稻茬烤烟主栽品种上部烟叶烘烤特性存在差异,在制定烘烤工艺时要区别对待。

关键词：烤烟变黄变褐失水叶绿素降解多酚氧化酶活性

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